I thought gamekings had guilding metal jackets, which has some copper content, as all do. The barns should be a nightmare in your rifle if it fouls bad with gamekings. You may want to try the Tubbs final finish treatment on your barrel. I haven't tried it but it's supposed to smoothe and polish the bore of your rifle, while only wearing the bore by .0001, which you can't measure anyhow. The process is advertised to decrease fouling, and improve accuracy at the same time. It's available from www.midwayusa.com and possiably from others. It's a simplified method of lapping the bore.